The present invention relates to a new and improved construction of apparatus for applying solder to different circuit boards, generally referred to herein broadly as simply printed-circuit boards.
In its more particular aspects, the apparatus for the application of a solder layer or covering to the metalized surfaces of a horizontally advanced printed-circuit board, utilizes a supply container or receptacle containing molten solder and a substantially chimney-like solder applicator structure or solder applicator device which protrudes out of such supply container. The solder is upwardly pumped out of the supply container through the solder applicator device in such a manner that a wave of liquid solder is formed over an outlet or discharge opening of the solder applicator device which is directed into contact with the printed-circuit board. At the upper edge of both of the side walls of the solder applicator or applying device, and which side walls extend transversely with respect to the feed or advance direction of the printed-circuit boards, there are arranged guide elements formed of metal plating or sheet metal. These guide elements can be adjusted as to their angle of inclination with respect to the feed plane of the printed-circuit boards which extends at a certain spacing above the discharge opening of the solder applicator device, the solder of the solder wave flowing back by means of these guide elements into the supply container.
A soldering apparatus of the aforementioned type is disclosed in U.S. Pat. No. 2,993,272, granted July 25, 1961, and serves for soldering electrical components to printed-circuit boards. The circuit boards which contain the electrical components are continuously horizontally guided over the solder wave and the bottom face or underside of such circuit boards along with the terminals of the electrical components are coated with solder. During the fabrication of circuit boards for printed-circuits it is advantageous to provide, prior to the mounting of the electrical components, a protective solderable coating at the metallic surfaces appearing at both the top and bottom faces of the circuit boards and also at the bore or drill holes, and thus, to improve the shelf life properties thereof and to also prepare the circuit boards such that their soldering properties are enhanced.
In European Patent Application No. 1-0013359 there is disclosed an apparatus which renders possible, during horizontal passage of the circuit boards, the application of a solder layer into the bore or drill holes and also to both faces of a circuit board which is not yet equipped with the electrical components, in contrast to the heretofore known technique of vertically immersing the circuit boards into a molten solder bath. This equipment consists of a first container from which liquid solder is pumped into a second container in such a quantity that there is formed in the second container a solder bath level which continuously lies above horizontally extending slot-shaped openings. These slot-shaped openings are provided at oppositely situated walls of the second container and are located in the feed or advance plane of the printed-circuit boards. The printed-circuit boards which are to be equipped with the electrical components are displaced by means of the slot-shaped openings through a static column of liquid solder and thus coated with solder.